18 |
|
* but supporting more flexible usage. |
19 |
|
* |
20 |
|
* <p> <b>Registration.</b> Unlike the case for other barriers, the |
21 |
< |
* number of parties <em>registered</em> to synchronize on a Phaser |
21 |
> |
* number of parties <em>registered</em> to synchronize on a phaser |
22 |
|
* may vary over time. Tasks may be registered at any time (using |
23 |
|
* methods {@link #register}, {@link #bulkRegister}, or forms of |
24 |
|
* constructors establishing initial numbers of parties), and |
34 |
|
* Phaser} may be repeatedly awaited. Method {@link |
35 |
|
* #arriveAndAwaitAdvance} has effect analogous to {@link |
36 |
|
* java.util.concurrent.CyclicBarrier#await CyclicBarrier.await}. Each |
37 |
< |
* generation of a {@code Phaser} has an associated phase number. The |
38 |
< |
* phase number starts at zero, and advances when all parties arrive |
39 |
< |
* at the barrier, wrapping around to zero after reaching {@code |
37 |
> |
* generation of a phaser has an associated phase number. The phase |
38 |
> |
* number starts at zero, and advances when all parties arrive at the |
39 |
> |
* phaser, wrapping around to zero after reaching {@code |
40 |
|
* Integer.MAX_VALUE}. The use of phase numbers enables independent |
41 |
< |
* control of actions upon arrival at a barrier and upon awaiting |
41 |
> |
* control of actions upon arrival at a phaser and upon awaiting |
42 |
|
* others, via two kinds of methods that may be invoked by any |
43 |
|
* registered party: |
44 |
|
* |
45 |
|
* <ul> |
46 |
|
* |
47 |
|
* <li> <b>Arrival.</b> Methods {@link #arrive} and |
48 |
< |
* {@link #arriveAndDeregister} record arrival at a |
49 |
< |
* barrier. These methods do not block, but return an associated |
50 |
< |
* <em>arrival phase number</em>; that is, the phase number of |
51 |
< |
* the barrier to which the arrival applied. When the final |
52 |
< |
* party for a given phase arrives, an optional barrier action |
53 |
< |
* is performed and the phase advances. Barrier actions, |
54 |
< |
* performed by the party triggering a phase advance, are |
55 |
< |
* arranged by overriding method {@link #onAdvance(int, int)}, |
56 |
< |
* which also controls termination. Overriding this method is |
57 |
< |
* similar to, but more flexible than, providing a barrier |
58 |
< |
* action to a {@code CyclicBarrier}. |
48 |
> |
* {@link #arriveAndDeregister} record arrival. These methods |
49 |
> |
* do not block, but return an associated <em>arrival phase |
50 |
> |
* number</em>; that is, the phase number of the phaser to which |
51 |
> |
* the arrival applied. When the final party for a given phase |
52 |
> |
* arrives, an optional action is performed and the phase |
53 |
> |
* advances. These actions are performed by the party |
54 |
> |
* triggering a phase advance, and are arranged by overriding |
55 |
> |
* method {@link #onAdvance(int, int)}, which also controls |
56 |
> |
* termination. Overriding this method is similar to, but more |
57 |
> |
* flexible than, providing a barrier action to a {@code |
58 |
> |
* CyclicBarrier}. |
59 |
|
* |
60 |
|
* <li> <b>Waiting.</b> Method {@link #awaitAdvance} requires an |
61 |
|
* argument indicating an arrival phase number, and returns when |
62 |
< |
* the barrier advances to (or is already at) a different phase. |
62 |
> |
* the phaser advances to (or is already at) a different phase. |
63 |
|
* Unlike similar constructions using {@code CyclicBarrier}, |
64 |
|
* method {@code awaitAdvance} continues to wait even if the |
65 |
|
* waiting thread is interrupted. Interruptible and timeout |
66 |
|
* versions are also available, but exceptions encountered while |
67 |
|
* tasks wait interruptibly or with timeout do not change the |
68 |
< |
* state of the barrier. If necessary, you can perform any |
68 |
> |
* state of the phaser. If necessary, you can perform any |
69 |
|
* associated recovery within handlers of those exceptions, |
70 |
|
* often after invoking {@code forceTermination}. Phasers may |
71 |
|
* also be used by tasks executing in a {@link ForkJoinPool}, |
74 |
|
* |
75 |
|
* </ul> |
76 |
|
* |
77 |
< |
* <p> <b>Termination.</b> A {@code Phaser} may enter a |
78 |
< |
* <em>termination</em> state in which all synchronization methods |
79 |
< |
* immediately return without updating Phaser state or waiting for |
80 |
< |
* advance, and indicating (via a negative phase value) that execution |
81 |
< |
* is complete. Termination is triggered when an invocation of {@code |
82 |
< |
* onAdvance} returns {@code true}. The default implementation returns |
83 |
< |
* {@code true} if a deregistration has caused the number of |
84 |
< |
* registered parties to become zero. As illustrated below, when |
85 |
< |
* Phasers control actions with a fixed number of iterations, it is |
86 |
< |
* often convenient to override this method to cause termination when |
87 |
< |
* the current phase number reaches a threshold. Method {@link |
88 |
< |
* #forceTermination} is also available to abruptly release waiting |
89 |
< |
* threads and allow them to terminate. |
77 |
> |
* <p> <b>Termination.</b> A phaser may enter a <em>termination</em> |
78 |
> |
* state, that may be checked using method {@link #isTerminated}. Upon |
79 |
> |
* termination, all synchronization methods immediately return without |
80 |
> |
* waiting for advance, as indicated by a negative return value. |
81 |
> |
* Similarly, attempts to register upon termination have no effect. |
82 |
> |
* Termination is triggered when an invocation of {@code onAdvance} |
83 |
> |
* returns {@code true}. The default implementation returns {@code |
84 |
> |
* true} if a deregistration has caused the number of registered |
85 |
> |
* parties to become zero. As illustrated below, when phasers control |
86 |
> |
* actions with a fixed number of iterations, it is often convenient |
87 |
> |
* to override this method to cause termination when the current phase |
88 |
> |
* number reaches a threshold. Method {@link #forceTermination} is |
89 |
> |
* also available to abruptly release waiting threads and allow them |
90 |
> |
* to terminate. |
91 |
|
* |
92 |
|
* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., |
93 |
|
* constructed in tree structures) to reduce contention. Phasers with |
97 |
|
* increase throughput even though it incurs greater per-operation |
98 |
|
* overhead. |
99 |
|
* |
100 |
+ |
* <p>In a tree of tiered phasers, registration and deregistration of |
101 |
+ |
* child phasers with their parent are managed automatically. |
102 |
+ |
* Whenever the number of registered parties of a child phaser becomes |
103 |
+ |
* non-zero (as established in the {@link #Phaser(Phaser,int)} |
104 |
+ |
* constructor, {@link #register}, or {@link #bulkRegister}), the |
105 |
+ |
* child phaser is registered with its parent. Whenever the number of |
106 |
+ |
* registered parties becomes zero as the result of an invocation of |
107 |
+ |
* {@link #arriveAndDeregister}, the child phaser is deregistered |
108 |
+ |
* from its parent. |
109 |
+ |
* |
110 |
|
* <p><b>Monitoring.</b> While synchronization methods may be invoked |
111 |
< |
* only by registered parties, the current state of a Phaser may be |
111 |
> |
* only by registered parties, the current state of a phaser may be |
112 |
|
* monitored by any caller. At any given moment there are {@link |
113 |
|
* #getRegisteredParties} parties in total, of which {@link |
114 |
|
* #getArrivedParties} have arrived at the current phase ({@link |
194 |
|
* }}</pre> |
195 |
|
* |
196 |
|
* |
197 |
< |
* <p>To create a set of tasks using a tree of Phasers, |
198 |
< |
* you could use code of the following form, assuming a |
199 |
< |
* Task class with a constructor accepting a Phaser that |
200 |
< |
* it registers with upon construction: |
197 |
> |
* <p>To create a set of {@code n} tasks using a tree of phasers, you |
198 |
> |
* could use code of the following form, assuming a Task class with a |
199 |
> |
* constructor accepting a {@code Phaser} that it registers with upon |
200 |
> |
* construction. After invocation of {@code build(new Task[n], 0, n, |
201 |
> |
* new Phaser())}, these tasks could then be started, for example by |
202 |
> |
* submitting to a pool: |
203 |
|
* |
204 |
|
* <pre> {@code |
205 |
< |
* void build(Task[] actions, int lo, int hi, Phaser ph) { |
205 |
> |
* void build(Task[] tasks, int lo, int hi, Phaser ph) { |
206 |
|
* if (hi - lo > TASKS_PER_PHASER) { |
207 |
|
* for (int i = lo; i < hi; i += TASKS_PER_PHASER) { |
208 |
|
* int j = Math.min(i + TASKS_PER_PHASER, hi); |
209 |
< |
* build(actions, i, j, new Phaser(ph)); |
209 |
> |
* build(tasks, i, j, new Phaser(ph)); |
210 |
|
* } |
211 |
|
* } else { |
212 |
|
* for (int i = lo; i < hi; ++i) |
213 |
< |
* actions[i] = new Task(ph); |
213 |
> |
* tasks[i] = new Task(ph); |
214 |
|
* // assumes new Task(ph) performs ph.register() |
215 |
|
* } |
216 |
< |
* } |
204 |
< |
* // .. initially called, for n tasks via |
205 |
< |
* build(new Task[n], 0, n, new Phaser());}</pre> |
216 |
> |
* }}</pre> |
217 |
|
* |
218 |
|
* The best value of {@code TASKS_PER_PHASER} depends mainly on |
219 |
< |
* expected barrier synchronization rates. A value as low as four may |
220 |
< |
* be appropriate for extremely small per-barrier task bodies (thus |
219 |
> |
* expected synchronization rates. A value as low as four may |
220 |
> |
* be appropriate for extremely small per-phase task bodies (thus |
221 |
|
* high rates), or up to hundreds for extremely large ones. |
222 |
|
* |
223 |
|
* <p><b>Implementation notes</b>: This implementation restricts the |
224 |
|
* maximum number of parties to 65535. Attempts to register additional |
225 |
|
* parties result in {@code IllegalStateException}. However, you can and |
226 |
< |
* should create tiered Phasers to accommodate arbitrarily large sets |
226 |
> |
* should create tiered phasers to accommodate arbitrarily large sets |
227 |
|
* of participants. |
228 |
|
* |
229 |
|
* @since 1.7 |
237 |
|
*/ |
238 |
|
|
239 |
|
/** |
240 |
< |
* Barrier state representation. Conceptually, a barrier contains |
230 |
< |
* four values: |
240 |
> |
* Primary state representation, holding four fields: |
241 |
|
* |
242 |
|
* * unarrived -- the number of parties yet to hit barrier (bits 0-15) |
243 |
|
* * parties -- the number of parties to wait (bits 16-31) |
244 |
|
* * phase -- the generation of the barrier (bits 32-62) |
245 |
|
* * terminated -- set if barrier is terminated (bit 63 / sign) |
246 |
|
* |
247 |
< |
* However, to efficiently maintain atomicity, these values are |
248 |
< |
* packed into a single (atomic) long. Termination uses the sign |
249 |
< |
* bit of 32 bit representation of phase, so phase is set to -1 on |
250 |
< |
* termination. Good performance relies on keeping state decoding |
251 |
< |
* and encoding simple, and keeping race windows short. |
247 |
> |
* Except that a phaser with no registered parties is |
248 |
> |
* distinguished with the otherwise illegal state of having zero |
249 |
> |
* parties and one unarrived parties (encoded as EMPTY below). |
250 |
> |
* |
251 |
> |
* To efficiently maintain atomicity, these values are packed into |
252 |
> |
* a single (atomic) long. Good performance relies on keeping |
253 |
> |
* state decoding and encoding simple, and keeping race windows |
254 |
> |
* short. |
255 |
> |
* |
256 |
> |
* All state updates are performed via CAS except initial |
257 |
> |
* registration of a sub-phaser (i.e., one with a non-null |
258 |
> |
* parent). In this (relatively rare) case, we use built-in |
259 |
> |
* synchronization to lock while first registering with its |
260 |
> |
* parent. |
261 |
> |
* |
262 |
> |
* The phase of a subphaser is allowed to lag that of its |
263 |
> |
* ancestors until it is actually accessed -- see method |
264 |
> |
* reconcileState. |
265 |
|
*/ |
266 |
|
private volatile long state; |
267 |
|
|
269 |
|
private static final int MAX_PHASE = 0x7fffffff; |
270 |
|
private static final int PARTIES_SHIFT = 16; |
271 |
|
private static final int PHASE_SHIFT = 32; |
272 |
+ |
private static final long PHASE_MASK = -1L << PHASE_SHIFT; |
273 |
|
private static final int UNARRIVED_MASK = 0xffff; // to mask ints |
274 |
|
private static final long PARTIES_MASK = 0xffff0000L; // to mask longs |
251 |
– |
private static final long ONE_ARRIVAL = 1L; |
252 |
– |
private static final long ONE_PARTY = 1L << PARTIES_SHIFT; |
275 |
|
private static final long TERMINATION_BIT = 1L << 63; |
276 |
|
|
277 |
+ |
// some special values |
278 |
+ |
private static final int ONE_ARRIVAL = 1; |
279 |
+ |
private static final int ONE_PARTY = 1 << PARTIES_SHIFT; |
280 |
+ |
private static final int EMPTY = 1; |
281 |
+ |
|
282 |
|
// The following unpacking methods are usually manually inlined |
283 |
|
|
284 |
|
private static int unarrivedOf(long s) { |
285 |
< |
return (int)s & UNARRIVED_MASK; |
285 |
> |
int counts = (int)s; |
286 |
> |
return (counts == EMPTY) ? 0 : counts & UNARRIVED_MASK; |
287 |
|
} |
288 |
|
|
289 |
|
private static int partiesOf(long s) { |
295 |
|
} |
296 |
|
|
297 |
|
private static int arrivedOf(long s) { |
298 |
< |
return partiesOf(s) - unarrivedOf(s); |
298 |
> |
int counts = (int)s; |
299 |
> |
return (counts == EMPTY) ? 0 : |
300 |
> |
(counts >>> PARTIES_SHIFT) - (counts & UNARRIVED_MASK); |
301 |
|
} |
302 |
|
|
303 |
|
/** |
306 |
|
private final Phaser parent; |
307 |
|
|
308 |
|
/** |
309 |
< |
* The root of phaser tree. Equals this if not in a tree. Used to |
280 |
< |
* support faster state push-down. |
309 |
> |
* The root of phaser tree. Equals this if not in a tree. |
310 |
|
*/ |
311 |
|
private final Phaser root; |
312 |
|
|
344 |
|
* Manually tuned to speed up and minimize race windows for the |
345 |
|
* common case of just decrementing unarrived field. |
346 |
|
* |
347 |
< |
* @param adj - adjustment to apply to state -- either |
319 |
< |
* ONE_ARRIVAL (for arrive) or |
320 |
< |
* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister) |
347 |
> |
* @param deregister false for arrive, true for arriveAndDeregister |
348 |
|
*/ |
349 |
< |
private int doArrive(long adj) { |
349 |
> |
private int doArrive(boolean deregister) { |
350 |
> |
int adj = deregister ? ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL; |
351 |
> |
final Phaser root = this.root; |
352 |
|
for (;;) { |
353 |
< |
long s = state; |
325 |
< |
int unarrived = (int)s & UNARRIVED_MASK; |
353 |
> |
long s = (root == this) ? state : reconcileState(); |
354 |
|
int phase = (int)(s >>> PHASE_SHIFT); |
355 |
+ |
int counts = (int)s; |
356 |
+ |
int unarrived = (counts & UNARRIVED_MASK) - 1; |
357 |
|
if (phase < 0) |
358 |
|
return phase; |
359 |
< |
else if (unarrived == 0) { |
360 |
< |
if (reconcileState() == s) // recheck |
359 |
> |
else if (counts == EMPTY || unarrived < 0) { |
360 |
> |
if (root == this || reconcileState() == s) |
361 |
|
throw new IllegalStateException(badArrive(s)); |
362 |
|
} |
363 |
|
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) { |
364 |
< |
if (unarrived == 1) { |
365 |
< |
long p = s & PARTIES_MASK; // unshifted parties field |
366 |
< |
long lu = p >>> PARTIES_SHIFT; |
367 |
< |
int u = (int)lu; |
368 |
< |
int nextPhase = (phase + 1) & MAX_PHASE; |
369 |
< |
long next = ((long)nextPhase << PHASE_SHIFT) | p | lu; |
370 |
< |
final Phaser parent = this.parent; |
371 |
< |
if (parent == null) { |
372 |
< |
if (onAdvance(phase, u)) |
373 |
< |
next |= TERMINATION_BIT; |
374 |
< |
UNSAFE.compareAndSwapLong(this, stateOffset, s, next); |
375 |
< |
releaseWaiters(phase); |
376 |
< |
} |
377 |
< |
else { |
348 |
< |
parent.doArrive((u == 0) ? |
349 |
< |
ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL); |
350 |
< |
if ((int)(parent.state >>> PHASE_SHIFT) != nextPhase || |
351 |
< |
((int)(state >>> PHASE_SHIFT) != nextPhase && |
352 |
< |
!UNSAFE.compareAndSwapLong(this, stateOffset, |
353 |
< |
s, next))) |
354 |
< |
reconcileState(); |
355 |
< |
} |
364 |
> |
if (unarrived == 0) { |
365 |
> |
long n = s & PARTIES_MASK; // base of next state |
366 |
> |
int nextUnarrived = ((int)n) >>> PARTIES_SHIFT; |
367 |
> |
if (root != this) |
368 |
> |
return parent.doArrive(nextUnarrived == 0); |
369 |
> |
if (onAdvance(phase, nextUnarrived)) |
370 |
> |
n |= TERMINATION_BIT; |
371 |
> |
else if (nextUnarrived == 0) |
372 |
> |
n |= EMPTY; |
373 |
> |
else |
374 |
> |
n |= nextUnarrived; |
375 |
> |
n |= ((long)((phase + 1) & MAX_PHASE)) << PHASE_SHIFT; |
376 |
> |
UNSAFE.compareAndSwapLong(this, stateOffset, s, n); |
377 |
> |
releaseWaiters(phase); |
378 |
|
} |
379 |
|
return phase; |
380 |
|
} |
390 |
|
private int doRegister(int registrations) { |
391 |
|
// adjustment to state |
392 |
|
long adj = ((long)registrations << PARTIES_SHIFT) | registrations; |
393 |
< |
final Phaser parent = this.parent; |
393 |
> |
Phaser par = parent; |
394 |
> |
int phase; |
395 |
|
for (;;) { |
396 |
< |
long s = (parent == null) ? state : reconcileState(); |
397 |
< |
int parties = (int)s >>> PARTIES_SHIFT; |
398 |
< |
int phase = (int)(s >>> PHASE_SHIFT); |
399 |
< |
if (phase < 0) |
400 |
< |
return phase; |
378 |
< |
else if (registrations > MAX_PARTIES - parties) |
396 |
> |
long s = state; |
397 |
> |
int counts = (int)s; |
398 |
> |
int parties = counts >>> PARTIES_SHIFT; |
399 |
> |
int unarrived = counts & UNARRIVED_MASK; |
400 |
> |
if (registrations > MAX_PARTIES - parties) |
401 |
|
throw new IllegalStateException(badRegister(s)); |
402 |
< |
else if ((parties == 0 && parent == null) || // first reg of root |
403 |
< |
((int)s & UNARRIVED_MASK) != 0) { // not advancing |
404 |
< |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj)) |
405 |
< |
return phase; |
406 |
< |
} |
407 |
< |
else if (parties != 0) // wait for onAdvance |
408 |
< |
root.internalAwaitAdvance(phase, null); |
409 |
< |
else { // 1st registration of child |
410 |
< |
synchronized(this) { // register parent first |
411 |
< |
if (reconcileState() == s) { // recheck under lock |
412 |
< |
parent.doRegister(1); // OK if throws IllegalState |
413 |
< |
for (;;) { // simpler form of outer loop |
414 |
< |
s = reconcileState(); |
415 |
< |
phase = (int)(s >>> PHASE_SHIFT); |
416 |
< |
if (phase < 0 || |
417 |
< |
UNSAFE.compareAndSwapLong(this, stateOffset, |
418 |
< |
s, s + adj)) |
419 |
< |
return phase; |
420 |
< |
} |
402 |
> |
else if ((phase = (int)(s >>> PHASE_SHIFT)) < 0) |
403 |
> |
break; |
404 |
> |
else if (counts != EMPTY) { // not 1st registration |
405 |
> |
if (par == null || reconcileState() == s) { |
406 |
> |
if (unarrived == 0) // wait out advance |
407 |
> |
root.internalAwaitAdvance(phase, null); |
408 |
> |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, |
409 |
> |
s, s + adj)) |
410 |
> |
break; |
411 |
> |
} |
412 |
> |
} |
413 |
> |
else if (par == null) { // 1st root registration |
414 |
> |
long next = (((long) phase) << PHASE_SHIFT) | adj; |
415 |
> |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) |
416 |
> |
break; |
417 |
> |
} |
418 |
> |
else { |
419 |
> |
synchronized (this) { // 1st sub registration |
420 |
> |
if (state == s) { // recheck under lock |
421 |
> |
par.doRegister(1); |
422 |
> |
do { // force current phase |
423 |
> |
phase = (int)(root.state >>> PHASE_SHIFT); |
424 |
> |
// assert phase < 0 || (int)state == EMPTY; |
425 |
> |
} while (!UNSAFE.compareAndSwapLong |
426 |
> |
(this, stateOffset, state, |
427 |
> |
(((long) phase) << PHASE_SHIFT) | adj)); |
428 |
> |
break; |
429 |
|
} |
430 |
|
} |
431 |
|
} |
432 |
|
} |
433 |
+ |
return phase; |
434 |
|
} |
435 |
|
|
436 |
|
/** |
437 |
< |
* Recursively resolves lagged phase propagation from root if necessary. |
437 |
> |
* Resolves lagged phase propagation from root if necessary. |
438 |
> |
* Reconciliation normally occurs when root has advanced but |
439 |
> |
* subphasers have not yet done so, in which case they must finish |
440 |
> |
* their own advance by setting unarrived to parties (or if |
441 |
> |
* parties is zero, resetting to unregistered EMPTY state). |
442 |
> |
* However, this method may also be called when "floating" |
443 |
> |
* subphasers with possibly some unarrived parties are merely |
444 |
> |
* catching up to current phase, in which case counts are |
445 |
> |
* unaffected. |
446 |
> |
* |
447 |
> |
* @return reconciled state |
448 |
|
*/ |
449 |
|
private long reconcileState() { |
450 |
< |
Phaser par = parent; |
450 |
> |
final Phaser root = this.root; |
451 |
|
long s = state; |
452 |
< |
if (par != null) { |
453 |
< |
Phaser rt = root; |
454 |
< |
int phase, rPhase; |
455 |
< |
while ((phase = (int)(s >>> PHASE_SHIFT)) >= 0 && |
456 |
< |
(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) { |
457 |
< |
if ((int)(par.state >>> PHASE_SHIFT) != rPhase) |
458 |
< |
par.reconcileState(); |
459 |
< |
else if (rPhase < 0 || ((int)s & UNARRIVED_MASK) == 0) { |
460 |
< |
long u = s & PARTIES_MASK; // reset unarrived to parties |
461 |
< |
long next = ((((long) rPhase) << PHASE_SHIFT) | u | |
421 |
< |
(u >>> PARTIES_SHIFT)); |
422 |
< |
UNSAFE.compareAndSwapLong(this, stateOffset, s, next); |
423 |
< |
} |
452 |
> |
if (root != this) { |
453 |
> |
int phase, u, p; |
454 |
> |
// CAS root phase with current parties; possibly trip unarrived |
455 |
> |
while ((phase = (int)(root.state >>> PHASE_SHIFT)) != |
456 |
> |
(int)(s >>> PHASE_SHIFT) && |
457 |
> |
!UNSAFE.compareAndSwapLong |
458 |
> |
(this, stateOffset, s, |
459 |
> |
s = ((((long) phase) << PHASE_SHIFT) | (s & PARTIES_MASK) | |
460 |
> |
((p = (int)s >>> PARTIES_SHIFT) == 0 ? EMPTY : |
461 |
> |
(u = (int)s & UNARRIVED_MASK) == 0 ? p : u)))) |
462 |
|
s = state; |
425 |
– |
} |
463 |
|
} |
464 |
|
return s; |
465 |
|
} |
466 |
|
|
467 |
|
/** |
468 |
< |
* Creates a new Phaser without any initially registered parties, |
469 |
< |
* initial phase number 0, and no parent. Any thread using this |
470 |
< |
* Phaser will need to first register for it. |
468 |
> |
* Creates a new phaser with no initially registered parties, no |
469 |
> |
* parent, and initial phase number 0. Any thread using this |
470 |
> |
* phaser will need to first register for it. |
471 |
|
*/ |
472 |
|
public Phaser() { |
473 |
|
this(null, 0); |
474 |
|
} |
475 |
|
|
476 |
|
/** |
477 |
< |
* Creates a new Phaser with the given number of registered |
478 |
< |
* unarrived parties, initial phase number 0, and no parent. |
477 |
> |
* Creates a new phaser with the given number of registered |
478 |
> |
* unarrived parties, no parent, and initial phase number 0. |
479 |
|
* |
480 |
< |
* @param parties the number of parties required to trip barrier |
480 |
> |
* @param parties the number of parties required to advance to the |
481 |
> |
* next phase |
482 |
|
* @throws IllegalArgumentException if parties less than zero |
483 |
|
* or greater than the maximum number of parties supported |
484 |
|
*/ |
489 |
|
/** |
490 |
|
* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}. |
491 |
|
* |
492 |
< |
* @param parent the parent Phaser |
492 |
> |
* @param parent the parent phaser |
493 |
|
*/ |
494 |
|
public Phaser(Phaser parent) { |
495 |
|
this(parent, 0); |
496 |
|
} |
497 |
|
|
498 |
|
/** |
499 |
< |
* Creates a new Phaser with the given parent and number of |
500 |
< |
* registered unarrived parties. Registration and deregistration |
501 |
< |
* of this child Phaser with its parent are managed automatically. |
502 |
< |
* If the given parent is non-null, whenever this child Phaser has |
503 |
< |
* any registered parties (as established in this constructor, |
504 |
< |
* {@link #register}, or {@link #bulkRegister}), this child Phaser |
505 |
< |
* is registered with its parent. Whenever the number of |
506 |
< |
* registered parties becomes zero as the result of an invocation |
469 |
< |
* of {@link #arriveAndDeregister}, this child Phaser is |
470 |
< |
* deregistered from its parent. |
471 |
< |
* |
472 |
< |
* @param parent the parent Phaser |
473 |
< |
* @param parties the number of parties required to trip barrier |
499 |
> |
* Creates a new phaser with the given parent and number of |
500 |
> |
* registered unarrived parties. When the given parent is non-null |
501 |
> |
* and the given number of parties is greater than zero, this |
502 |
> |
* child phaser is registered with its parent. |
503 |
> |
* |
504 |
> |
* @param parent the parent phaser |
505 |
> |
* @param parties the number of parties required to advance to the |
506 |
> |
* next phase |
507 |
|
* @throws IllegalArgumentException if parties less than zero |
508 |
|
* or greater than the maximum number of parties supported |
509 |
|
*/ |
510 |
|
public Phaser(Phaser parent, int parties) { |
511 |
|
if (parties >>> PARTIES_SHIFT != 0) |
512 |
|
throw new IllegalArgumentException("Illegal number of parties"); |
513 |
< |
long s = ((long) parties) | (((long) parties) << PARTIES_SHIFT); |
513 |
> |
int phase = 0; |
514 |
|
this.parent = parent; |
515 |
|
if (parent != null) { |
516 |
< |
Phaser r = parent.root; |
517 |
< |
this.root = r; |
518 |
< |
this.evenQ = r.evenQ; |
519 |
< |
this.oddQ = r.oddQ; |
516 |
> |
final Phaser root = parent.root; |
517 |
> |
this.root = root; |
518 |
> |
this.evenQ = root.evenQ; |
519 |
> |
this.oddQ = root.oddQ; |
520 |
|
if (parties != 0) |
521 |
< |
s |= ((long)(parent.doRegister(1))) << PHASE_SHIFT; |
521 |
> |
phase = parent.doRegister(1); |
522 |
|
} |
523 |
|
else { |
524 |
|
this.root = this; |
525 |
|
this.evenQ = new AtomicReference<QNode>(); |
526 |
|
this.oddQ = new AtomicReference<QNode>(); |
527 |
|
} |
528 |
< |
this.state = s; |
528 |
> |
this.state = (parties == 0) ? (long) EMPTY : |
529 |
> |
((((long) phase) << PHASE_SHIFT) | |
530 |
> |
(((long) parties) << PARTIES_SHIFT) | |
531 |
> |
((long) parties)); |
532 |
|
} |
533 |
|
|
534 |
|
/** |
535 |
< |
* Adds a new unarrived party to this Phaser. If an ongoing |
535 |
> |
* Adds a new unarrived party to this phaser. If an ongoing |
536 |
|
* invocation of {@link #onAdvance} is in progress, this method |
537 |
< |
* may await its completion before returning. If this Phaser has |
538 |
< |
* a parent, and this Phaser previously had no registered parties, |
539 |
< |
* this Phaser is also registered with its parent. |
540 |
< |
* |
541 |
< |
* @return the arrival phase number to which this registration applied |
537 |
> |
* may await its completion before returning. If this phaser has |
538 |
> |
* a parent, and this phaser previously had no registered parties, |
539 |
> |
* this child phaser is also registered with its parent. If |
540 |
> |
* this phaser is terminated, the attempt to register has |
541 |
> |
* no effect, and a negative value is returned. |
542 |
> |
* |
543 |
> |
* @return the arrival phase number to which this registration |
544 |
> |
* applied. If this value is negative, then this phaser has |
545 |
> |
* terminated, in which case registration has no effect. |
546 |
|
* @throws IllegalStateException if attempting to register more |
547 |
|
* than the maximum supported number of parties |
548 |
|
*/ |
551 |
|
} |
552 |
|
|
553 |
|
/** |
554 |
< |
* Adds the given number of new unarrived parties to this Phaser. |
554 |
> |
* Adds the given number of new unarrived parties to this phaser. |
555 |
|
* If an ongoing invocation of {@link #onAdvance} is in progress, |
556 |
|
* this method may await its completion before returning. If this |
557 |
< |
* Phaser has a parent, and the given number of parities is |
558 |
< |
* greater than zero, and this Phaser previously had no registered |
559 |
< |
* parties, this Phaser is also registered with its parent. |
560 |
< |
* |
561 |
< |
* @param parties the number of additional parties required to trip barrier |
562 |
< |
* @return the arrival phase number to which this registration applied |
557 |
> |
* phaser has a parent, and the given number of parties is greater |
558 |
> |
* than zero, and this phaser previously had no registered |
559 |
> |
* parties, this child phaser is also registered with its parent. |
560 |
> |
* If this phaser is terminated, the attempt to register has no |
561 |
> |
* effect, and a negative value is returned. |
562 |
> |
* |
563 |
> |
* @param parties the number of additional parties required to |
564 |
> |
* advance to the next phase |
565 |
> |
* @return the arrival phase number to which this registration |
566 |
> |
* applied. If this value is negative, then this phaser has |
567 |
> |
* terminated, in which case registration has no effect. |
568 |
|
* @throws IllegalStateException if attempting to register more |
569 |
|
* than the maximum supported number of parties |
570 |
|
* @throws IllegalArgumentException if {@code parties < 0} |
578 |
|
} |
579 |
|
|
580 |
|
/** |
581 |
< |
* Arrives at the barrier, without waiting for others to arrive. |
581 |
> |
* Arrives at this phaser, without waiting for others to arrive. |
582 |
|
* |
583 |
|
* <p>It is a usage error for an unregistered party to invoke this |
584 |
|
* method. However, this error may result in an {@code |
585 |
|
* IllegalStateException} only upon some subsequent operation on |
586 |
< |
* this Phaser, if ever. |
586 |
> |
* this phaser, if ever. |
587 |
|
* |
588 |
|
* @return the arrival phase number, or a negative value if terminated |
589 |
|
* @throws IllegalStateException if not terminated and the number |
590 |
|
* of unarrived parties would become negative |
591 |
|
*/ |
592 |
|
public int arrive() { |
593 |
< |
return doArrive(ONE_ARRIVAL); |
593 |
> |
return doArrive(false); |
594 |
|
} |
595 |
|
|
596 |
|
/** |
597 |
< |
* Arrives at the barrier and deregisters from it without waiting |
597 |
> |
* Arrives at this phaser and deregisters from it without waiting |
598 |
|
* for others to arrive. Deregistration reduces the number of |
599 |
< |
* parties required to trip the barrier in future phases. If this |
600 |
< |
* Phaser has a parent, and deregistration causes this Phaser to |
601 |
< |
* have zero parties, this Phaser is also deregistered from its |
557 |
< |
* parent. |
599 |
> |
* parties required to advance in future phases. If this phaser |
600 |
> |
* has a parent, and deregistration causes this phaser to have |
601 |
> |
* zero parties, this phaser is also deregistered from its parent. |
602 |
|
* |
603 |
|
* <p>It is a usage error for an unregistered party to invoke this |
604 |
|
* method. However, this error may result in an {@code |
605 |
|
* IllegalStateException} only upon some subsequent operation on |
606 |
< |
* this Phaser, if ever. |
606 |
> |
* this phaser, if ever. |
607 |
|
* |
608 |
|
* @return the arrival phase number, or a negative value if terminated |
609 |
|
* @throws IllegalStateException if not terminated and the number |
610 |
|
* of registered or unarrived parties would become negative |
611 |
|
*/ |
612 |
|
public int arriveAndDeregister() { |
613 |
< |
return doArrive(ONE_ARRIVAL|ONE_PARTY); |
613 |
> |
return doArrive(true); |
614 |
|
} |
615 |
|
|
616 |
|
/** |
617 |
< |
* Arrives at the barrier and awaits others. Equivalent in effect |
617 |
> |
* Arrives at this phaser and awaits others. Equivalent in effect |
618 |
|
* to {@code awaitAdvance(arrive())}. If you need to await with |
619 |
|
* interruption or timeout, you can arrange this with an analogous |
620 |
|
* construction using one of the other forms of the {@code |
624 |
|
* <p>It is a usage error for an unregistered party to invoke this |
625 |
|
* method. However, this error may result in an {@code |
626 |
|
* IllegalStateException} only upon some subsequent operation on |
627 |
< |
* this Phaser, if ever. |
627 |
> |
* this phaser, if ever. |
628 |
|
* |
629 |
< |
* @return the arrival phase number, or a negative number if terminated |
629 |
> |
* @return the arrival phase number, or the (negative) |
630 |
> |
* {@linkplain #getPhase() current phase} if terminated |
631 |
|
* @throws IllegalStateException if not terminated and the number |
632 |
|
* of unarrived parties would become negative |
633 |
|
*/ |
634 |
|
public int arriveAndAwaitAdvance() { |
635 |
< |
return awaitAdvance(arrive()); |
635 |
> |
// Specialization of doArrive+awaitAdvance eliminating some reads/paths |
636 |
> |
final Phaser root = this.root; |
637 |
> |
for (;;) { |
638 |
> |
long s = (root == this) ? state : reconcileState(); |
639 |
> |
int phase = (int)(s >>> PHASE_SHIFT); |
640 |
> |
int counts = (int)s; |
641 |
> |
int unarrived = (counts & UNARRIVED_MASK) - 1; |
642 |
> |
if (phase < 0) |
643 |
> |
return phase; |
644 |
> |
else if (counts == EMPTY || unarrived < 0) { |
645 |
> |
if (reconcileState() == s) |
646 |
> |
throw new IllegalStateException(badArrive(s)); |
647 |
> |
} |
648 |
> |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, |
649 |
> |
s -= ONE_ARRIVAL)) { |
650 |
> |
if (unarrived != 0) |
651 |
> |
return root.internalAwaitAdvance(phase, null); |
652 |
> |
if (root != this) |
653 |
> |
return parent.arriveAndAwaitAdvance(); |
654 |
> |
long n = s & PARTIES_MASK; // base of next state |
655 |
> |
int nextUnarrived = ((int)n) >>> PARTIES_SHIFT; |
656 |
> |
if (onAdvance(phase, nextUnarrived)) |
657 |
> |
n |= TERMINATION_BIT; |
658 |
> |
else if (nextUnarrived == 0) |
659 |
> |
n |= EMPTY; |
660 |
> |
else |
661 |
> |
n |= nextUnarrived; |
662 |
> |
int nextPhase = (phase + 1) & MAX_PHASE; |
663 |
> |
n |= (long)nextPhase << PHASE_SHIFT; |
664 |
> |
if (!UNSAFE.compareAndSwapLong(this, stateOffset, s, n)) |
665 |
> |
return (int)(state >>> PHASE_SHIFT); // terminated |
666 |
> |
releaseWaiters(phase); |
667 |
> |
return nextPhase; |
668 |
> |
} |
669 |
> |
} |
670 |
|
} |
671 |
|
|
672 |
|
/** |
673 |
< |
* Awaits the phase of the barrier to advance from the given phase |
674 |
< |
* value, returning immediately if the current phase of the |
675 |
< |
* barrier is not equal to the given phase value or this barrier |
597 |
< |
* is terminated. |
673 |
> |
* Awaits the phase of this phaser to advance from the given phase |
674 |
> |
* value, returning immediately if the current phase is not equal |
675 |
> |
* to the given phase value or this phaser is terminated. |
676 |
|
* |
677 |
|
* @param phase an arrival phase number, or negative value if |
678 |
|
* terminated; this argument is normally the value returned by a |
679 |
< |
* previous call to {@code arrive} or its variants |
680 |
< |
* @return the next arrival phase number, or a negative value |
681 |
< |
* if terminated or argument is negative |
679 |
> |
* previous call to {@code arrive} or {@code arriveAndDeregister}. |
680 |
> |
* @return the next arrival phase number, or the argument if it is |
681 |
> |
* negative, or the (negative) {@linkplain #getPhase() current phase} |
682 |
> |
* if terminated |
683 |
|
*/ |
684 |
|
public int awaitAdvance(int phase) { |
685 |
< |
Phaser r; |
686 |
< |
int p = (int)(state >>> PHASE_SHIFT); |
685 |
> |
final Phaser root = this.root; |
686 |
> |
long s = (root == this) ? state : reconcileState(); |
687 |
> |
int p = (int)(s >>> PHASE_SHIFT); |
688 |
|
if (phase < 0) |
689 |
|
return phase; |
690 |
< |
if (p == phase && |
691 |
< |
(p = (int)((r = root).state >>> PHASE_SHIFT)) == phase) |
612 |
< |
return r.internalAwaitAdvance(phase, null); |
690 |
> |
if (p == phase) |
691 |
> |
return root.internalAwaitAdvance(phase, null); |
692 |
|
return p; |
693 |
|
} |
694 |
|
|
695 |
|
/** |
696 |
< |
* Awaits the phase of the barrier to advance from the given phase |
696 |
> |
* Awaits the phase of this phaser to advance from the given phase |
697 |
|
* value, throwing {@code InterruptedException} if interrupted |
698 |
< |
* while waiting, or returning immediately if the current phase of |
699 |
< |
* the barrier is not equal to the given phase value or this |
700 |
< |
* barrier is terminated. |
698 |
> |
* while waiting, or returning immediately if the current phase is |
699 |
> |
* not equal to the given phase value or this phaser is |
700 |
> |
* terminated. |
701 |
|
* |
702 |
|
* @param phase an arrival phase number, or negative value if |
703 |
|
* terminated; this argument is normally the value returned by a |
704 |
< |
* previous call to {@code arrive} or its variants |
705 |
< |
* @return the next arrival phase number, or a negative value |
706 |
< |
* if terminated or argument is negative |
704 |
> |
* previous call to {@code arrive} or {@code arriveAndDeregister}. |
705 |
> |
* @return the next arrival phase number, or the argument if it is |
706 |
> |
* negative, or the (negative) {@linkplain #getPhase() current phase} |
707 |
> |
* if terminated |
708 |
|
* @throws InterruptedException if thread interrupted while waiting |
709 |
|
*/ |
710 |
|
public int awaitAdvanceInterruptibly(int phase) |
711 |
|
throws InterruptedException { |
712 |
< |
Phaser r; |
713 |
< |
int p = (int)(state >>> PHASE_SHIFT); |
712 |
> |
final Phaser root = this.root; |
713 |
> |
long s = (root == this) ? state : reconcileState(); |
714 |
> |
int p = (int)(s >>> PHASE_SHIFT); |
715 |
|
if (phase < 0) |
716 |
|
return phase; |
717 |
< |
if (p == phase && |
637 |
< |
(p = (int)((r = root).state >>> PHASE_SHIFT)) == phase) { |
717 |
> |
if (p == phase) { |
718 |
|
QNode node = new QNode(this, phase, true, false, 0L); |
719 |
< |
p = r.internalAwaitAdvance(phase, node); |
719 |
> |
p = root.internalAwaitAdvance(phase, node); |
720 |
|
if (node.wasInterrupted) |
721 |
|
throw new InterruptedException(); |
722 |
|
} |
724 |
|
} |
725 |
|
|
726 |
|
/** |
727 |
< |
* Awaits the phase of the barrier to advance from the given phase |
727 |
> |
* Awaits the phase of this phaser to advance from the given phase |
728 |
|
* value or the given timeout to elapse, throwing {@code |
729 |
|
* InterruptedException} if interrupted while waiting, or |
730 |
< |
* returning immediately if the current phase of the barrier is |
731 |
< |
* not equal to the given phase value or this barrier is |
652 |
< |
* terminated. |
730 |
> |
* returning immediately if the current phase is not equal to the |
731 |
> |
* given phase value or this phaser is terminated. |
732 |
|
* |
733 |
|
* @param phase an arrival phase number, or negative value if |
734 |
|
* terminated; this argument is normally the value returned by a |
735 |
< |
* previous call to {@code arrive} or its variants |
735 |
> |
* previous call to {@code arrive} or {@code arriveAndDeregister}. |
736 |
|
* @param timeout how long to wait before giving up, in units of |
737 |
|
* {@code unit} |
738 |
|
* @param unit a {@code TimeUnit} determining how to interpret the |
739 |
|
* {@code timeout} parameter |
740 |
< |
* @return the next arrival phase number, or a negative value |
741 |
< |
* if terminated or argument is negative |
740 |
> |
* @return the next arrival phase number, or the argument if it is |
741 |
> |
* negative, or the (negative) {@linkplain #getPhase() current phase} |
742 |
> |
* if terminated |
743 |
|
* @throws InterruptedException if thread interrupted while waiting |
744 |
|
* @throws TimeoutException if timed out while waiting |
745 |
|
*/ |
747 |
|
long timeout, TimeUnit unit) |
748 |
|
throws InterruptedException, TimeoutException { |
749 |
|
long nanos = unit.toNanos(timeout); |
750 |
< |
Phaser r; |
751 |
< |
int p = (int)(state >>> PHASE_SHIFT); |
750 |
> |
final Phaser root = this.root; |
751 |
> |
long s = (root == this) ? state : reconcileState(); |
752 |
> |
int p = (int)(s >>> PHASE_SHIFT); |
753 |
|
if (phase < 0) |
754 |
|
return phase; |
755 |
< |
if (p == phase && |
675 |
< |
(p = (int)((r = root).state >>> PHASE_SHIFT)) == phase) { |
755 |
> |
if (p == phase) { |
756 |
|
QNode node = new QNode(this, phase, true, true, nanos); |
757 |
< |
p = r.internalAwaitAdvance(phase, node); |
757 |
> |
p = root.internalAwaitAdvance(phase, node); |
758 |
|
if (node.wasInterrupted) |
759 |
|
throw new InterruptedException(); |
760 |
|
else if (p == phase) |
764 |
|
} |
765 |
|
|
766 |
|
/** |
767 |
< |
* Forces this barrier to enter termination state. Counts of |
768 |
< |
* arrived and registered parties are unaffected. If this Phaser |
769 |
< |
* is a member of a tiered set of Phasers, then all of the Phasers |
770 |
< |
* in the set are terminated. If this Phaser is already |
771 |
< |
* terminated, this method has no effect. This method may be |
772 |
< |
* useful for coordinating recovery after one or more tasks |
773 |
< |
* encounter unexpected exceptions. |
767 |
> |
* Forces this phaser to enter termination state. Counts of |
768 |
> |
* registered parties are unaffected. If this phaser is a member |
769 |
> |
* of a tiered set of phasers, then all of the phasers in the set |
770 |
> |
* are terminated. If this phaser is already terminated, this |
771 |
> |
* method has no effect. This method may be useful for |
772 |
> |
* coordinating recovery after one or more tasks encounter |
773 |
> |
* unexpected exceptions. |
774 |
|
*/ |
775 |
|
public void forceTermination() { |
776 |
|
// Only need to change root state |
779 |
|
while ((s = root.state) >= 0) { |
780 |
|
if (UNSAFE.compareAndSwapLong(root, stateOffset, |
781 |
|
s, s | TERMINATION_BIT)) { |
782 |
< |
releaseWaiters(0); // signal all threads |
782 |
> |
// signal all threads |
783 |
> |
releaseWaiters(0); |
784 |
|
releaseWaiters(1); |
785 |
|
return; |
786 |
|
} |
790 |
|
/** |
791 |
|
* Returns the current phase number. The maximum phase number is |
792 |
|
* {@code Integer.MAX_VALUE}, after which it restarts at |
793 |
< |
* zero. Upon termination, the phase number is negative. |
793 |
> |
* zero. Upon termination, the phase number is negative, |
794 |
> |
* in which case the prevailing phase prior to termination |
795 |
> |
* may be obtained via {@code getPhase() + Integer.MIN_VALUE}. |
796 |
|
* |
797 |
|
* @return the phase number, or a negative value if terminated |
798 |
|
*/ |
801 |
|
} |
802 |
|
|
803 |
|
/** |
804 |
< |
* Returns the number of parties registered at this barrier. |
804 |
> |
* Returns the number of parties registered at this phaser. |
805 |
|
* |
806 |
|
* @return the number of parties |
807 |
|
*/ |
811 |
|
|
812 |
|
/** |
813 |
|
* Returns the number of registered parties that have arrived at |
814 |
< |
* the current phase of this barrier. |
814 |
> |
* the current phase of this phaser. If this phaser has terminated, |
815 |
> |
* the returned value is meaningless and arbitrary. |
816 |
|
* |
817 |
|
* @return the number of arrived parties |
818 |
|
*/ |
819 |
|
public int getArrivedParties() { |
820 |
< |
long s = state; |
737 |
< |
int u = unarrivedOf(s); // only reconcile if possibly needed |
738 |
< |
return (u != 0 || parent == null) ? |
739 |
< |
partiesOf(s) - u : |
740 |
< |
arrivedOf(reconcileState()); |
820 |
> |
return arrivedOf(reconcileState()); |
821 |
|
} |
822 |
|
|
823 |
|
/** |
824 |
|
* Returns the number of registered parties that have not yet |
825 |
< |
* arrived at the current phase of this barrier. |
825 |
> |
* arrived at the current phase of this phaser. If this phaser has |
826 |
> |
* terminated, the returned value is meaningless and arbitrary. |
827 |
|
* |
828 |
|
* @return the number of unarrived parties |
829 |
|
*/ |
830 |
|
public int getUnarrivedParties() { |
831 |
< |
int u = unarrivedOf(state); |
751 |
< |
return (u != 0 || parent == null) ? u : unarrivedOf(reconcileState()); |
831 |
> |
return unarrivedOf(reconcileState()); |
832 |
|
} |
833 |
|
|
834 |
|
/** |
835 |
< |
* Returns the parent of this Phaser, or {@code null} if none. |
835 |
> |
* Returns the parent of this phaser, or {@code null} if none. |
836 |
|
* |
837 |
< |
* @return the parent of this Phaser, or {@code null} if none |
837 |
> |
* @return the parent of this phaser, or {@code null} if none |
838 |
|
*/ |
839 |
|
public Phaser getParent() { |
840 |
|
return parent; |
841 |
|
} |
842 |
|
|
843 |
|
/** |
844 |
< |
* Returns the root ancestor of this Phaser, which is the same as |
845 |
< |
* this Phaser if it has no parent. |
844 |
> |
* Returns the root ancestor of this phaser, which is the same as |
845 |
> |
* this phaser if it has no parent. |
846 |
|
* |
847 |
< |
* @return the root ancestor of this Phaser |
847 |
> |
* @return the root ancestor of this phaser |
848 |
|
*/ |
849 |
|
public Phaser getRoot() { |
850 |
|
return root; |
851 |
|
} |
852 |
|
|
853 |
|
/** |
854 |
< |
* Returns {@code true} if this barrier has been terminated. |
854 |
> |
* Returns {@code true} if this phaser has been terminated. |
855 |
|
* |
856 |
< |
* @return {@code true} if this barrier has been terminated |
856 |
> |
* @return {@code true} if this phaser has been terminated |
857 |
|
*/ |
858 |
|
public boolean isTerminated() { |
859 |
|
return root.state < 0L; |
862 |
|
/** |
863 |
|
* Overridable method to perform an action upon impending phase |
864 |
|
* advance, and to control termination. This method is invoked |
865 |
< |
* upon arrival of the party tripping the barrier (when all other |
865 |
> |
* upon arrival of the party advancing this phaser (when all other |
866 |
|
* waiting parties are dormant). If this method returns {@code |
867 |
< |
* true}, then, rather than advance the phase number, this barrier |
868 |
< |
* will be set to a final termination state, and subsequent calls |
869 |
< |
* to {@link #isTerminated} will return true. Any (unchecked) |
870 |
< |
* Exception or Error thrown by an invocation of this method is |
871 |
< |
* propagated to the party attempting to trip the barrier, in |
872 |
< |
* which case no advance occurs. |
867 |
> |
* true}, this phaser will be set to a final termination state |
868 |
> |
* upon advance, and subsequent calls to {@link #isTerminated} |
869 |
> |
* will return true. Any (unchecked) Exception or Error thrown by |
870 |
> |
* an invocation of this method is propagated to the party |
871 |
> |
* attempting to advance this phaser, in which case no advance |
872 |
> |
* occurs. |
873 |
|
* |
874 |
< |
* <p>The arguments to this method provide the state of the Phaser |
874 |
> |
* <p>The arguments to this method provide the state of the phaser |
875 |
|
* prevailing for the current transition. The effects of invoking |
876 |
< |
* arrival, registration, and waiting methods on this Phaser from |
876 |
> |
* arrival, registration, and waiting methods on this phaser from |
877 |
|
* within {@code onAdvance} are unspecified and should not be |
878 |
|
* relied on. |
879 |
|
* |
880 |
< |
* <p>If this Phaser is a member of a tiered set of Phasers, then |
881 |
< |
* {@code onAdvance} is invoked only for its root Phaser on each |
880 |
> |
* <p>If this phaser is a member of a tiered set of phasers, then |
881 |
> |
* {@code onAdvance} is invoked only for its root phaser on each |
882 |
|
* advance. |
883 |
|
* |
884 |
|
* <p>To support the most common use cases, the default |
894 |
|
* protected boolean onAdvance(int phase, int parties) { return false; } |
895 |
|
* }}</pre> |
896 |
|
* |
897 |
< |
* @param phase the phase number on entering the barrier |
897 |
> |
* @param phase the current phase number on entry to this method, |
898 |
> |
* before this phaser is advanced |
899 |
|
* @param registeredParties the current number of registered parties |
900 |
< |
* @return {@code true} if this barrier should terminate |
900 |
> |
* @return {@code true} if this phaser should terminate |
901 |
|
*/ |
902 |
|
protected boolean onAdvance(int phase, int registeredParties) { |
903 |
< |
return registeredParties <= 0; |
903 |
> |
return registeredParties == 0; |
904 |
|
} |
905 |
|
|
906 |
|
/** |
907 |
< |
* Returns a string identifying this Phaser, as well as its |
907 |
> |
* Returns a string identifying this phaser, as well as its |
908 |
|
* state. The state, in brackets, includes the String {@code |
909 |
|
* "phase = "} followed by the phase number, {@code "parties = "} |
910 |
|
* followed by the number of registered parties, and {@code |
911 |
|
* "arrived = "} followed by the number of arrived parties. |
912 |
|
* |
913 |
< |
* @return a string identifying this barrier, as well as its state |
913 |
> |
* @return a string identifying this phaser, as well as its state |
914 |
|
*/ |
915 |
|
public String toString() { |
916 |
|
return stateToString(reconcileState()); |
932 |
|
* Removes and signals threads from queue for phase. |
933 |
|
*/ |
934 |
|
private void releaseWaiters(int phase) { |
935 |
< |
AtomicReference<QNode> head = queueFor(phase); |
936 |
< |
QNode q; |
937 |
< |
int p; |
935 |
> |
QNode q; // first element of queue |
936 |
> |
Thread t; // its thread |
937 |
> |
AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ; |
938 |
|
while ((q = head.get()) != null && |
939 |
< |
((p = q.phase) == phase || |
940 |
< |
(int)(root.state >>> PHASE_SHIFT) != p)) { |
941 |
< |
if (head.compareAndSet(q, q.next)) |
942 |
< |
q.signal(); |
939 |
> |
q.phase != (int)(root.state >>> PHASE_SHIFT)) { |
940 |
> |
if (head.compareAndSet(q, q.next) && |
941 |
> |
(t = q.thread) != null) { |
942 |
> |
q.thread = null; |
943 |
> |
LockSupport.unpark(t); |
944 |
> |
} |
945 |
> |
} |
946 |
> |
} |
947 |
> |
|
948 |
> |
/** |
949 |
> |
* Variant of releaseWaiters that additionally tries to remove any |
950 |
> |
* nodes no longer waiting for advance due to timeout or |
951 |
> |
* interrupt. Currently, nodes are removed only if they are at |
952 |
> |
* head of queue, which suffices to reduce memory footprint in |
953 |
> |
* most usages. |
954 |
> |
* |
955 |
> |
* @return current phase on exit |
956 |
> |
*/ |
957 |
> |
private int abortWait(int phase) { |
958 |
> |
AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ; |
959 |
> |
for (;;) { |
960 |
> |
Thread t; |
961 |
> |
QNode q = head.get(); |
962 |
> |
int p = (int)(root.state >>> PHASE_SHIFT); |
963 |
> |
if (q == null || ((t = q.thread) != null && q.phase == p)) |
964 |
> |
return p; |
965 |
> |
if (head.compareAndSet(q, q.next) && t != null) { |
966 |
> |
q.thread = null; |
967 |
> |
LockSupport.unpark(t); |
968 |
> |
} |
969 |
|
} |
970 |
|
} |
971 |
|
|
980 |
|
* avoid it when threads regularly arrive: When a thread in |
981 |
|
* internalAwaitAdvance notices another arrival before blocking, |
982 |
|
* and there appear to be enough CPUs available, it spins |
983 |
< |
* SPINS_PER_ARRIVAL more times before blocking. Plus, even on |
984 |
< |
* uniprocessors, there is at least one intervening Thread.yield |
878 |
< |
* before blocking. The value trades off good-citizenship vs big |
879 |
< |
* unnecessary slowdowns. |
983 |
> |
* SPINS_PER_ARRIVAL more times before blocking. The value trades |
984 |
> |
* off good-citizenship vs big unnecessary slowdowns. |
985 |
|
*/ |
986 |
|
static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8; |
987 |
|
|
995 |
|
* @return current phase |
996 |
|
*/ |
997 |
|
private int internalAwaitAdvance(int phase, QNode node) { |
998 |
< |
boolean queued = false; // true when node is enqueued |
999 |
< |
int lastUnarrived = -1; // to increase spins upon change |
998 |
> |
releaseWaiters(phase-1); // ensure old queue clean |
999 |
> |
boolean queued = false; // true when node is enqueued |
1000 |
> |
int lastUnarrived = 0; // to increase spins upon change |
1001 |
|
int spins = SPINS_PER_ARRIVAL; |
1002 |
|
long s; |
1003 |
|
int p; |
1004 |
|
while ((p = (int)((s = state) >>> PHASE_SHIFT)) == phase) { |
1005 |
< |
int unarrived = (int)s & UNARRIVED_MASK; |
1006 |
< |
if (unarrived != lastUnarrived) { |
1007 |
< |
if (lastUnarrived == -1) // ensure old queue clean |
1008 |
< |
releaseWaiters(phase-1); |
903 |
< |
if ((lastUnarrived = unarrived) < NCPU) |
1005 |
> |
if (node == null) { // spinning in noninterruptible mode |
1006 |
> |
int unarrived = (int)s & UNARRIVED_MASK; |
1007 |
> |
if (unarrived != lastUnarrived && |
1008 |
> |
(lastUnarrived = unarrived) < NCPU) |
1009 |
|
spins += SPINS_PER_ARRIVAL; |
1010 |
< |
} |
1011 |
< |
else if (spins > 0) { |
1012 |
< |
if (--spins == (SPINS_PER_ARRIVAL >>> 1)) |
1013 |
< |
Thread.yield(); // yield midway through spin |
909 |
< |
} |
910 |
< |
else if (node == null) // must be noninterruptible |
911 |
< |
node = new QNode(this, phase, false, false, 0L); |
912 |
< |
else if (node.isReleasable()) { |
913 |
< |
p = (int)(state >>> PHASE_SHIFT); |
914 |
< |
break; // aborted |
915 |
< |
} |
916 |
< |
else if (!queued) { // push onto queue |
917 |
< |
AtomicReference<QNode> head = queueFor(phase); |
918 |
< |
QNode q = head.get(); |
919 |
< |
if (q == null || q.phase == phase) { |
920 |
< |
node.next = q; |
921 |
< |
if ((p = (int)(state >>> PHASE_SHIFT)) != phase) |
922 |
< |
break; // recheck to avoid stale enqueue |
923 |
< |
else |
924 |
< |
queued = head.compareAndSet(q, node); |
1010 |
> |
boolean interrupted = Thread.interrupted(); |
1011 |
> |
if (interrupted || --spins < 0) { // need node to record intr |
1012 |
> |
node = new QNode(this, phase, false, false, 0L); |
1013 |
> |
node.wasInterrupted = interrupted; |
1014 |
|
} |
1015 |
|
} |
1016 |
+ |
else if (node.isReleasable()) // done or aborted |
1017 |
+ |
break; |
1018 |
+ |
else if (!queued) { // push onto queue |
1019 |
+ |
AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ; |
1020 |
+ |
QNode q = node.next = head.get(); |
1021 |
+ |
if ((q == null || q.phase == phase) && |
1022 |
+ |
(int)(state >>> PHASE_SHIFT) == phase) // avoid stale enq |
1023 |
+ |
queued = head.compareAndSet(q, node); |
1024 |
+ |
} |
1025 |
|
else { |
1026 |
|
try { |
1027 |
|
ForkJoinPool.managedBlock(node); |
1033 |
|
|
1034 |
|
if (node != null) { |
1035 |
|
if (node.thread != null) |
1036 |
< |
node.thread = null; // disable unpark() in node.signal |
1037 |
< |
if (!node.interruptible && node.wasInterrupted) |
1036 |
> |
node.thread = null; // avoid need for unpark() |
1037 |
> |
if (node.wasInterrupted && !node.interruptible) |
1038 |
|
Thread.currentThread().interrupt(); |
1039 |
+ |
if (p == phase && (p = (int)(state >>> PHASE_SHIFT)) == phase) |
1040 |
+ |
return abortWait(phase); // possibly clean up on abort |
1041 |
|
} |
1042 |
< |
if (p != phase) |
943 |
< |
releaseWaiters(phase); |
1042 |
> |
releaseWaiters(phase); |
1043 |
|
return p; |
1044 |
|
} |
1045 |
|
|
1064 |
|
this.interruptible = interruptible; |
1065 |
|
this.nanos = nanos; |
1066 |
|
this.timed = timed; |
1067 |
< |
this.lastTime = timed? System.nanoTime() : 0L; |
1067 |
> |
this.lastTime = timed ? System.nanoTime() : 0L; |
1068 |
|
thread = Thread.currentThread(); |
1069 |
|
} |
1070 |
|
|
1071 |
|
public boolean isReleasable() { |
1072 |
< |
Thread t = thread; |
1073 |
< |
if (t != null) { |
1074 |
< |
if (phaser.getPhase() != phase) |
1075 |
< |
t = null; |
1076 |
< |
else { |
1077 |
< |
if (Thread.interrupted()) |
1078 |
< |
wasInterrupted = true; |
1079 |
< |
if (interruptible && wasInterrupted) |
1080 |
< |
t = null; |
982 |
< |
else if (timed) { |
983 |
< |
if (nanos > 0) { |
984 |
< |
long now = System.nanoTime(); |
985 |
< |
nanos -= now - lastTime; |
986 |
< |
lastTime = now; |
987 |
< |
} |
988 |
< |
if (nanos <= 0) |
989 |
< |
t = null; |
990 |
< |
} |
991 |
< |
} |
992 |
< |
if (t != null) |
993 |
< |
return false; |
1072 |
> |
if (thread == null) |
1073 |
> |
return true; |
1074 |
> |
if (phaser.getPhase() != phase) { |
1075 |
> |
thread = null; |
1076 |
> |
return true; |
1077 |
> |
} |
1078 |
> |
if (Thread.interrupted()) |
1079 |
> |
wasInterrupted = true; |
1080 |
> |
if (wasInterrupted && interruptible) { |
1081 |
|
thread = null; |
1082 |
+ |
return true; |
1083 |
|
} |
1084 |
< |
return true; |
1084 |
> |
if (timed) { |
1085 |
> |
if (nanos > 0L) { |
1086 |
> |
long now = System.nanoTime(); |
1087 |
> |
nanos -= now - lastTime; |
1088 |
> |
lastTime = now; |
1089 |
> |
} |
1090 |
> |
if (nanos <= 0L) { |
1091 |
> |
thread = null; |
1092 |
> |
return true; |
1093 |
> |
} |
1094 |
> |
} |
1095 |
> |
return false; |
1096 |
|
} |
1097 |
|
|
1098 |
|
public boolean block() { |
1104 |
|
LockSupport.parkNanos(this, nanos); |
1105 |
|
return isReleasable(); |
1106 |
|
} |
1008 |
– |
|
1009 |
– |
void signal() { |
1010 |
– |
Thread t = thread; |
1011 |
– |
if (t != null) { |
1012 |
– |
thread = null; |
1013 |
– |
LockSupport.unpark(t); |
1014 |
– |
} |
1015 |
– |
} |
1107 |
|
} |
1108 |
|
|
1109 |
|
// Unsafe mechanics |